7 resultados para Reactions in Polar Aprotic Media

em Brock University, Canada


Relevância:

100.00% 100.00%

Publicador:

Resumo:

This study examined how perturbation-evoked compensatory arm reactions in individuals with Parkinson’s disease (PD) are influenced by explicit verbal instruction. Ten individuals with PD and 15 older adults without PD responded to surface translations with or without specific instruction to reach for and grasp the handrail. Electromyographic (EMG) and kinematic recordings were taken from the reaching arm. Results showed that individuals with and without PD benefitted similarly from explicit instruction. Explicit instruction resulted in earlier (p=0.005) and larger (p<0.001) medial deltoid EMG responses in comparison to no specific instructions. Compensatory arm reactions also occurred with a higher peak medio-lateral wrist velocity (p<0.001) and higher peak shoulder abduction angular velocity (p<0.001) with explicit instruction. Explicit instruction positively influenced compensatory arm reactions in individuals with and without PD. Future research is needed to determine whether the benefits of instruction persist over time and translate to a loss of balance in real life.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Part I: Ultra-trace determination of vanadium in lake sediments: a performance comparison using O2, N20, and NH3 as reaction gases in ICP-DRC-MS Thermal ion-molecule reactions, targeting removal of specific spectroscopic interference problems, have become a powerful tool for method development in quadrupole based inductively coupled plasma mass spectrometry (ICP-MS) applications. A study was conducted to develop an accurate method for the determination of vanadium in lake sediment samples by ICP-MS, coupled with a dynamic reaction cell (DRC), using two differenvchemical resolution strategies: a) direct removal of interfering C10+ and b) vanadium oxidation to VO+. The performance of three reaction gases that are suitable for handling vanadium interference in the dynamic reaction cell was systematically studied and evaluated: ammonia for C10+ removal and oxygen and nitrous oxide for oxidation. Although it was able to produce comparable results for vanadium to those using oxygen and nitrous oxide, NH3 did not completely eliminate a matrix effect, caused by the presence of chloride, and required large scale dilutions (and a concomitant increase in variance) when the sample and/or the digestion medium contained large amounts of chloride. Among the three candidate reaction gases at their optimized Eonditions, creation of VO+ with oxygen gas delivered the best analyte sensitivity and the lowest detection limit (2.7 ng L-1). Vanadium results obtained from fourteen lake sediment samples and a certified reference material (CRM031-040-1), using two different analytelinterference separation strategies, suggested that the vanadium mono-oxidation offers advantageous performance over the conventional method using NH3 for ultra-trace vanadium determination by ICP-DRC-MS and can be readily employed in relevant environmental chemistry applications that deal with ultra-trace contaminants.Part II: Validation of a modified oxidation approach for the quantification of total arsenic and selenium in complex environmental matrices Spectroscopic interference problems of arsenic and selenium in ICP-MS practices were investigated in detail. Preliminary literature review suggested that oxygen could serve as an effective candidate reaction gas for analysis of the two elements in dynamic reaction cell coupled ICP-MS. An accurate method was developed for the determination of As and Se in complex environmental samples, based on a series of modifications on an oxidation approach for As and Se previously reported. Rhodium was used as internal standard in this study to help minimize non-spectral interferences such as instrumental drift. Using an oxygen gas flow slightly higher than 0.5 mL min-I, arsenic is converted to 75 AS160+ ion in an efficient manner whereas a potentially interfering ion, 91Zr+, is completely removed. Instead of using the most abundant Se isotope, 80Se, selenium was determined by a second most abundant isotope, 78Se, in the form of 78Se160. Upon careful selection of oxygen gas flow rate and optimization ofRPq value, previous isobaric threats caused by Zr and Mo were reduced to background levels whereas another potential atomic isobar, 96Ru+, became completely harmless to the new selenium analyte. The new method underwent a strict validation procedure where the recovery of a suitable certified reference material was examined and the obtained sample data were compared with those produced by a credible external laboratory who analyzed the same set of samples using a standardized HG-ICP-AES method. The validation results were satisfactory. The resultant limits of detection for arsenic and selenium were 5 ng L-1 and 60 ng L-1, respectively.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Hydrogen bond assisted alkylation of phenols is compared with the classical base assisted reactions. The influence of solvents on the fluoride assisted reactions is discussed,· with emphasis on the localization of hydrogen bond charge density. Polar aprotic solvents such as DMF favour a-alkylation, and nonpolar aprotic solvents such as toluene favourC-alkylation of phenol. For more reactive and soluble fluorides, such as tetrabu~ylammoniumfluoride, the polar aprotic solvent favours a-alkylation and nonpolar aprotic solvent favours fluorination. Freeze-dried potassium fluoride is a better catalytic agent in hydrogen bond assisted alkylation reactions of phenol than the oven-dried fluoride. The presence of water in the alkylation reactions reduces the expected yield drastically. The tolerance of the reaction to water has also been studied. The use ofa phase transfer catalyst such as tetrabutylammonium bromide in the alkylation reactions of phenol in the presence of potassium fluoride is very effective under anhydrous conditions. Sterically hindered phenols such as 2,6-ditertiarybutyl-4-methyl phenol could not be alkylated even by using the more reactive fluorides, such as tetrabutylammonium fluoride in either polar or nonpolar aprotic solvents. Attempts were also made to alkylate phenols in the presence of triphenylphosphine oxide.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The past two centuries have witnessed the rise of nationalist movements and widespread nationalism. As these movements gained strength in Europe, sport played a role in their development. Media representations of sport recount events in a way that reinforces cultural values and this research investigates media representations of Croatian nationalism in the weeks surrounding the country’s third place victory in the 1998 FIFA World Cup. Sociological theories alongside more contemporary theories of sport and nation construction are considered. Croatian newspapers were analyzed for elements of national identity construction. The study concludes that the 1998 World Cup played an important role in Croatia’s on-going construction of nationhood and invention of nationalist traditions. This research further demonstrates sport’s ability to evoke strong emotions that are difficult to witness in other areas of social life and the direct role of sport in garnering nationalism.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Canadians appear to hold the activities of those in government and in big business in low esteem. Media reports of several high-profile political and corporate instances of unethical conduct have reinforced the public's concern for the status of ethical conduct and honesty in government and in big business. The response by public and private sector managers to unethical conduct by employees is largely in the form of 'ethical rules' which both sectors agree provide a measure of certainty as to the ethical conduct expected from employees. Since research on ethics in the public and private sectors is limited and since ethics is a topic of increasing concern to both sectors, this thesis provides data that could assist managers in dealing with the issue of ethical conduct within their respective organizations. The purpose of this thesis is to compare the state of ethical conduct within public and private sector organizations in Canada. This is accomplished through a description and analysis of the approaches taken by the public and private sectors as well as the four professions of law, engineering, accountancy and medicine. Ethical conduct within the public sector focuses on the ethical behaviour of public servants rather than elected officials. The underlying intent of this thesis is to discover if contemporary ethical problems are similar in the public and iv private sectors with respect to the four ethical areas of conflict of interest, political activity, problem public comment and confidentiality. The comparative data on both public and private sector ethics are assessed and similarities and differences are identified. One major finding emerges from this study. Codes of ethics in both the public and private sectors are perceived by management to play an important role in the prevention of unethical conduct. A procedure for developing a code of ethics is presented along with recommendations as to the administration of a code of ethics. Finally, recommendations are made as to the role of education in ethics.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The current dissertation examined role differences in the perception of injustice; specifically, differences in how victims and offenders respond to a situation that they both agree is unfair. Past research has demonstrated that role affects reactions to transgressions and injustice, including recall of transgressions, and attributions of blame and responsibility (e.g., Baumeister, Stillwell, & Wotman, 1990; Mikula, Athenstaedt, Heschgl, & Heimgartner, 1998). However, to date, little work has examined role differences in perceptions of why an event is perceived as unfair (i.e., how an injustice is framed) or how justice should be restored. These were the perceptions I focused on in the present thesis. I also examined potential concerns that may motivate victims' and offenders' justice reactions, as well as the potential interaction between role and relationship quality in predicting justice reactions. In Studies 1 and 2, several of the predicted role differences in concerns were found; however, these did not lead to the expected differences in framing and restoration. In Study 1, using a vignette methodology, I found differences primarily in how victims and offenders believed justice should be restored. Overall, the significant role effects showed an accommodating response pattern (e.g., offenders proposed punishment more than did victims and neutral observers, whereas victims recommended minimal compensation more than did offenders and neutral observers), inconsistent with previous research and my hypotheses. Study 2, which employed a sample of romantic couples, substantiated the accommodating pattern found in Study 1. Study 3, which sampled a broader range of relationships, also showed i \ examples of accommodating reactions. In addition, Study 3 provided some support for the hypothesized interaction between role and relationship quality, such that responses were more accommodating as relationship quality increased. For example, offenders more strongly endorsed methods of restoration such as offender apology and recognition of the relationship with increasing relationship quality. Overall, the results from this dissertation support the general notion that victims and offenders respond to injustice differently, and, in-line with previous research on other justice-related responses (e.g., Mikula et at, 1998), suggest that victims and offenders show an other-serving, accommodating tendency in justice reactions when relationship quality is high.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

This thesis describes syntheses and catalytic reactivity of several half-sandwich complexes of ruthenium. The neutral ruthenium trihydride complex, Cp(PPri3)RuH3(1), can efficiently catalyse the H/D exchange reaction between various organic substrates and deuterium sources, such as benzene-d6. Moreover, the H/D exchange reactions of polar substrates were also observed in D2O, which is the most attractive deuterium source due to its low cost and low toxicity. Importantly, the H/D exchange under catalytic conditions was achieved not only in aromatic compounds but also in substituted liphatic compounds. Interestingly, in the case of alkanes and alkyl chains, highly selective deuterium incorporation in the terminal methyl positions was observed. It was discovered that the methylene units are engaged in exchange only if the molecule contains a donating functional group, such as O-and N-donors, C=C double bonds, arenes and CH3. The cationic half-sandwich ruthenium complex [Cp(PPri3)Ru(CH3CN)2]+(2) catalyses the chemoselective mono-addition of HSiMe2Ph to pyridine derivatives to selectively give the 1,4-regiospecific, N-silylated products. An ionic hydrosilylation mechanismis suggested based on the experiments. To support this mechanistic proposal, kinetic studies under catalytic conditions were performed. Also, the 1,4-regioselective mono-hydrosilylation of nitrogen containing compounds such as phenanthroline, quinoline and acridine can be achieved with the related Cp*complex [Cp*(phen)Ru(CH3CN)]+(3) (phen = 1,10-phenanthroline) and HSiMe2Ph under mild conditions. The cationic ruthenium complex 2 can also be used as an efficient catalyst for transfer hydrogenation of various organic substrates including carbonyls, imines, nitriles and esters. Secondary alcohols, amines, N-isopropylidene amines and ether compounds can be obtained in moderate to high yields. In addition, other ruthenium complexes, 1,3 and [Cp*(PPri3)Ru(CH3CN)2]+(4), can catalyse transfer hydrogenation of carbonyls although the reactions were sluggish compared to the ones of 2. The possible intermediate, Cp(PPri3)Ru(CH3CN)(H), was characterized by NMR at low temperature and the kinetic studies for the transfer hydrogenation of acetophenone were performed. Recently, chemoselective reduction of acid chlorides to aldehydes catalysed by the complex 2 was reported. To extend the catalytic reactivity of 2, reduction of iminoyl chlorides, which can be readily obtained from secondary amides, to the corresponding imines and aldehydes was investigated. Various substituted iminoyl chlorides were converted into the imines and aldehydes under mild conditions and several products were isolated with moderate yields.